Important data files

I am working with the backup software SuperDuper. It allows you to back up a drive in bootable form and has other nice features similar to CCC and others. What is has different is a Safety Clone feature. This allows you to make a bootable copy of a drive that shares (via linking) certain data that remains on the original drive. What this does is allow you to load software and if you blow up your install, you can boot back on the other drive and not lose any data. I have set this up on my server in this fashion: Two 40G drives mirrored as primary volume. 120G drive partitioned into 40G & 70G w/40G set as Safety Clone of primary volume. Last partition used for backup. The Safety Clone is configured to "share" the Users Directory, mail, websites, & MySQL databases. I am wondering if I am missing anything. Right away I can see I am forgetting the Open Directory data which means if I add new users I will not have them if I go back to the primary volume. Any other thoughts?